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Mechanism of Corrosion by Naphthenic Acids and Organosulfur Compounds at High Temperatures

Jin, Peng
http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1384872234

Abstract Details

2013, Doctor of Philosophy (PhD), Ohio University, Chemical Engineering (Engineering and Technology).
Due to the law of supply and demand, the last decade has witnessed a skyrocketing in the price of light sweet crude oil. Therefore, refineries are increasingly interested in "opportunity crudes", characterized by their discounted price and relative ease of procurement. However, the attractive economics of opportunity crudes come with the disadvantage of high acid/organosulfur compound content, which could lead to corrosion and even failure of facilities in refineries. However, it is generally accepted that organosulfur compounds may form protective iron sulfide layers on the metal surface and decrease the corrosion rate. Therefore, it is necessary to investigate the corrosive property of crudes at high temperatures, the mechanism of corrosion by acids (naphthenic acids) in the presence of organosulfur compounds, and methods to mitigate its corrosive effect. In 2004, an industrial project was initiated at the Institute for Corrosion and Multiphase Technology to investigate the corrosion by naphthenic acids and organosulfur compounds. In this project, for each experiment there were two experimentation phases: pretreatment and challenge. In the first pretreatment phase, a stirred autoclave was filled with a real crude oil fraction or model oil of different acidity and organosulfur compound concentration. Then, the stirred autoclave was heated to high temperatures to examine the corrosivity of the oil to different materials (specimens made from CS and 5% Cr containing steel were used). During the pretreatment, corrosion product layers were formed on the metal surface. In the second challenge phase, the steel specimens pretreated in the first phase were inserted into a rotating cylinder autoclave, called High Velocity Rig (HVR). The HVR was fed with a high-temperature oil solution of naphthenic acids to attack the iron sulfide layers. Based on the difference of specimen weight loss between the two steps, the net corrosion rate could be calculated and the protectiveness of corrosion product layer against naphthenic acid corrosion could be assessed. Routinely, the layers generated in pretreatment and challenge phases were investigated with SEM/EDS (Scanning Electron Microscopy/Energy Dispersive Spectroscopy). Selectively, some thin layers formed in the first or second phase were analyzed with FIB-TEM (Focused Ion Beam - Transmission Electron Microscopy). FIB-TEM analysis revealed that there was an iron oxide layer beneath the iron sulfide layer. Experimental results showed that the iron oxide layer was closely related to the layer protectiveness against naphthenic acid corrosion and its formation was due to the presence of naphthenic acids in the fluid. Finally, a new mechanism of naphthenic acid/organosulfur compound corrosion was proposed based on properties of crudes, results of corrosion experimentation, and microscopic analysis of developed surface layers.
Srdjan Nesic (Committee Chair)
Martin Kordesch (Committee Member)
Valerie Young (Committee Member)
Eric Masson (Committee Member)
Monica Burdick (Committee Member)
231 p.
Chemical Engineering; Materials Science; Petroleum Engineering
naphthenic acids; high temperature corrosion; organosulfur compound; magnetite; crude fractions; TEM

Recommended Citations

Citations

  • Jin, P. (2013). Mechanism of Corrosion by Naphthenic Acids and Organosulfur Compounds at High Temperatures [Doctoral dissertation, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1384872234

    APA Style (7th edition)

  • Jin, Peng. Mechanism of Corrosion by Naphthenic Acids and Organosulfur Compounds at High Temperatures. 2013. Ohio University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1384872234.

    MLA Style (8th edition)

  • Jin, Peng. "Mechanism of Corrosion by Naphthenic Acids and Organosulfur Compounds at High Temperatures." Doctoral dissertation, Ohio University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1384872234

    Chicago Manual of Style (17th edition)

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This open access ETD is published by Ohio University and OhioLINK.